The density-matrix-renormalization group (DMRG) approach [1]}, [2]} has proven to be extremely useful in obtaining ground state correlations of Hubbard cylinders and ladders. As the computational effort grows roughly linearly with the length of the system, \(L\) , but exponentially with the number of legs, \(W\) , these results are largely confined to rather small \(W\) . However, for these systems, it provides an incomparably versatile approach to the intermediate coupling problem, without relying on any artificial limiting procedure.
